2018 - Biology Past Paper Corrections

Question 1

Give three ways a person with a mild infection of salmonella can help prevent the spread of bacteria to other people.

Answer 1

• Isolate yourself
• Disinfect surfaces
• Wash hands before handling food

Question 2

Explain why a person with AIDS may take longer than a healthy person to recover from a salmonella infection

Answer 2

• the immune system is damaged and weakened
• so the white blood cells cannot kill the salmonella bacteria as effectively

Question 3

Suggest two other ways farmers could prevent the transmission of salmonella from chickens to humans

Answer 3

• give chickens antibiotics
• keep infected chickens isolated

Question 4

Give one change to the investigation that would allow the scientist to check if the results are repeatable

Answer 4

repeat and look to see if results are similar

Question 5

Suggest one other factor the restaurant owner should consider when choosing which cleaning liquid to use

Answer 5

• toxicity
• health effects

Question 6

Explain why having more blood cells per cm3 of blood is an advantage to an athlete

Answer 6

• more haemoglobin
• therefore more oxygen can be transported
• for more aerobic respiration of muscle cells to release more energy

Question 7

Compare the structure of an artery with the structure of a vein

Answer 7

• arteries have a thicker layer of muscle tissue than veins
• arteries have a narrower lumen compared to veins
• arteries do not have valves, whereas veins do have valves

Question 8

What condition may be treated using an artificial pacemaker?

Answer 8

An irregular heartbeat

Question 9

Explain why masses of the eggs increased

Answer 9

• mass increased because water entered by osmosis
• from a dilute solution in the beaker to a more concentrated solution in the egg
• through a partially permeable membrane

Question 10

Give a reason why the mouthpiece of an aphid contains a high concentration of dissolved sugars after feeding

Answer 10

• because the mouthpiece has pierced the phloem

Question 10

Explain how a deficiency of magnesium could cause the symptoms of:
- yellow leaves
- stunted growth

Answer 10

• yellow leaves due to a lack of chlorophyll
• therefore less light is absorbed
• therefore a lower rate of photosynthesis
• therefore plant makes less glucose
• so plant converts less glucose into proteins, so growth is stunted

Question 11

Explain why children with CF grow more slowly than children without CF

Answer 11

• if the duct from the pancreas to the small intestine is blocked then fewer digestive enzymes enter the small intestine
• so enzymes break down/digest less food
• so therefore there is less absorption of nutrients
• so less glucose can enter the bloodstream
• so less glucose is available for respiration
• If the tubes leading to the alveoli in the lungs are blocked then less oxygen can reach the cells
• so less oxygen is available for aerobic respiration
• so less energy is released for growth

Question 12

Describe how the median age of a group of people can be determined

Answer 12

• put ages in ascending order
• find the middle value

Question 13

Suggest one reason why the median age for people with CF is lower than the median age for the whole population

Answer 13

it is most common in young people

Question 14

Give the reason why the measurement of the time taken for the indicator to become colourless might be inaccurate

Answer 14

observation of colour change is subjective/based on opinion

Question 15

How can starch be tested for?

Answer 15

• Iodine solution tests for starch
• Add iodine solution to whatever you are testing
• Solution will turn from orange/brown to blue/black if starch is present